1. Field of the Invention
This invention relates to a conveyor apparatus suitable for an escalator of a great height of story, a passenger-carrying conveyor of a great moving distance, or the like.
2. Description of the Related Art
Several structures of a conveyor apparatus capable of driving an escalator of a great height of story, a passenger-carrying conveyor of a great moving distance, or the like, by using a cheap standard chain, have been proposed.
FIG. 6 shows an example of a structure of a conventional conveyor apparatus.
The conveyor apparatus shown in FIG. 6 is an escalator. The escalator comprises a structure 1, a track 2, steps 3, chains 4 and three dispersed driving units 10a, 10b and 10c. 
The track 2 is provided to circulate around the structure 1. A plurality of steps 3 are moved along the track 2. The chains 4 are a pair of chains (at the front side and the back side of the figure) having pin rollers 4a which couple a plurality of steps 3 such that the steps circulate endlessly.
Three driving units 10a, 10b and 10c comprise rocking units 32, respectively. The rocking units 32 supply a propelling force to the chains 4. This technique is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-128441.
Since the driving units 10a, 10b and 10c have the same structure, the driving unit 10a alone is explained below as their typical example.
FIG. 7 shows a detailed structure of the driving unit 10a. 
The driving unit 10a comprises a power unit 20 which generates power, and chain driving mechanisms 30 which are arranged in pairs at right and left sides to sandwich the power unit 20. The power unit 20 has a motor 21 and a driving machine 22 which are attached to the structure 1.
The chain driving mechanisms 30 comprise eccentric shafts 31, the rocking units 32, trochoid-shaped rolling gears (hereinafter called trochoidal rolling gears) 33, and backside guide plates 34. The eccentric shafts 31 input rotation of the power unit 20. The rocking units 32 convert the rotation of the eccentric shafts 31 into rocking movement. The trochoidal rolling gears 33 engage with the pin rollers 4a which are attached to the chains 4 at regular intervals so as to be freely rotatable and supply the rocking movement of the rocking units 32 to the chains 4 as the propelling force.
The pin rollers 4a may be attached to the chains 4 at regular intervals or attached to the rocking units 32. The backside guide plates 34 guide the pin rollers 4a. 
Therefore, in the driving unit 10a having the above-described structure, if the rotary speed of the motor of the power unit 20 is made lower by the driving machine 22 to drive the eccentric shafts 31, the propelling force is supplied from the rocking units 32 to the chains 4 via the trochoidal rolling gears 33 engaging with the pin rollers 4a attached to the chains 4, and the steps 3 coupled to the chins 4 to circulate endlessly can be thereby moved at uniform velocity.
FIG. 8 shows a backside support structure of the chain 4 passing through the chain driving mechanism 30. A plurality of backside support rollers 35 which roll links 4b of the chain 4 are provided on the upper side of the trochoidal rolling gears 33, at a predetermined interval along the length direction of the chain 4. The backside support rollers 35 have a function of restricting flotage (N: see FIG. 8) of the links 4b which occurs when the trochoidal rolling gears 33 engage with the pin rollers 4a and propel the chain 4.
FIG. 9 shows a top view of the chain driving mechanism in the driving unit of another conventional conveyor apparatus. The entire structure of this conveyor apparatus is the same as that shown in FIG. 6. In the chain driving mechanism 30 of this conveyor apparatus, as shown in FIG. 9, however, a circular funicular body 36 is provided between the rocking unit 32 which executes the rocking movement by the operation of the motor 21 and the chain 4 and the rocking movement of the rocking unit 32 is converted into the circulating movement of the circular funicular body 36 to transfer the propelling force to the chain 4. The circular funicular body 36 comprises circulating rollers 36a, trochoid-shaped pin roller rolling internal gears 36b, and trochoid-shaped pin roller rolling external gears 36c. Rocking rollers 32a are provided between the rocking unit 32 and the pin roller rolling internal gears 36b. The rocking unit 32 is coupled to follower shafts 38. The follower shafts 38 eccentrically revolve when the eccentric shaft 31 eccentrically revolves.
In the above-described structure, a part which receives the rocking movement of the rocking unit 32 and a part which supplies the propelling force to the chain 4 are separated and independent in the chain driving mechanism 30 to attempt reducing the rocking. This technique is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-192263.
Incidentally, either of the above-described conveyor apparatuses must have the following functions and performance. FIG. 10 is a cross-sectional view of the conveyor apparatus, illustrating the arrangement of the driving unit 10a. 
At the middle part of the escalator, a step 3acarrying a passenger moves to an upper side of the structure (i.e. a forward side of FIG. 10) while a return-side step 3b moves to a lower side (i.e. a backward side of FIG. 10). At this time, a gap between the forward-side step and the backward-side step is approximately 300 to 400 mm. The power unit 20 comprising the motor 21 which drives the chain driving mechanism 30, and the like need to be installed in this gasp. In addition, noise caused by the power unit 20 needs to be so small as to give no uncomfortableness to passengers and surroundings.
If a safety device of the escalator detects an accident that the passenger is sandwiched between the steps 3, a failure of the driving unit 10a, and the like, movement of the steps 3 needs to be certainly stopped while reducing the influence to passengers to a minimum.
Moreover, the condition of the chain 4 and the engagement of the driving unit 10a with the chain 4 are regularly checked from the viewpoint of ensuring safety of the escalator. The steps 3 are detached at the checking operation. It is therefore desirable that the condition of the chain 4 and the engagement of the driving unit 10a with the chain 4 can be checked by merely detaching the steps 3. However, even if the steps 3 are detached, it is difficult to confirm tem due to disturbance of a number of members.
Furthermore, when the trochoidal rolling gears 33 and the circular funicular body 36 in the chain driving mechanism 30 engage with the pin rollers 4a of the chain 4 to propel the chain 4, the steps 3 are vibrated by impulse caused between the chain 4 and the backside support rollers 35. The vibration of the steps 3 must be so small as to give no uncomfortableness to passengers.
Furthermore, production of noise needs to be restricted at an escalator of a building where silence is considered very important, such as a hotel, a hospital and the like.